1. Field of the Invention
The present invention relates to a solid bonding method for bonding a metal and a metal, a metal and a ceramic, or other solid materials. More specifically, the present invention relates to a solid bonding method and apparatus for bonding a solid to a solid without melting a bonding agent or the bonded solids. The present invention further relates to a conductor bonding method, a packaging method, a bonding agent, and to a method for manufacturing a bonding agent.
2. Description of the Related Art
A common method of bonding two metals, such as copper to copper, or copper to aluminum, or two dissimilar solids such as a metal and ceramic, or metal and glass, is to use a bonding agent with a low melting point, such as solder or indium, to fuse the two solids together. A method more recently developed for bonding two metals involves placing the metals to be bonded in a vacuum chamber, irradiating the bonding surfaces of the metals with an ion beam to remove any surface oxides, and then heating and applying pressure to the metals to bond them together.
A common electronic component comprises a quartz oscillator or other electronic part vacuum sealed inside a ceramic or metallic package. During this packaging operation, the electronic component is typically placed in a bottom package cover in a vacuum environment, a top package cover is then placed on the package bottom, and the top and bottom are then bonded together. Bonding is accomplished by coating a soft metallic bonding agent with a low melting point, such as solder or indium, on the bonding surface of either the bottom or top cover. The covers are then placed together in a specific alignment and heat is applied to melt the low melting point bonding agent and fuse the top and bottom package parts together.
Japanese Unexamined Patent Publication (kokai) H1-270574 (1989-270574) teaches another method for bonding a ceramic and a ceramic, or a ceramic and a metal. In this method a ceramic is immersed in a molten halide-fluoride bath containing at least one of the following: a halide of an alkaline metal and an alkaline-earth metal, and a fluoride of an alkaline-earth metal. The bath is then heated to 700.degree. C. to 1100.degree. C., forming a non-oxide surface layer of, for example, a carbide, a boride, a nitride, or a silicide, on the surface of the ceramic. Two ceramic bodies with a non-oxide surface layer thus formed, or a metal and a ceramic with such a non-oxide surface layer, are then heated and bonded.
Japanese Unexamined Patent Publication (kokai) H10-36145 (1998-36145) teaches a method for bonding members of which a primary constituent of the bonding surface is silicon dioxide. In this method, the bonding surfaces of the members are permeated with a solution containing hydrofluoric acid to bond the members together.
A further technology described in the literature involves placing chrome bonding members in a high temperature fluoride gas environment at approximately 800.degree. C. to 900.degree. C., resulting in pyrolysis of the fluoride gas and fluorination of the bonding members. The members are then kept in this environment while being bonded.
Bonding solids with conventional soldering methods requires the use of flux, and typically must be followed by a washing process to remove sludge. In addition, when members are bonded by means of melting a bonding agent such as solder or indium, the alignment of the bond members is easily disturbed and controlling the final shape of the bonded articles during the bonding process is difficult. As a result, not only do shape inconsistencies occur, but the final appearance of the bonded article is poor.
It should be noted that shape inconsistencies and sludge problems also occur during bonding in the above-noted vacuum packaging methods because the bond is still established by melting a bonding agent.
It should be further noted that the above-noted bonding method in which surface oxides are removed from the bonded metals by exposure to an ion beam in a vacuum before bonding is not subject to these sludge problems and enables easier shape control because a bonding agent is not used. On the other hand, equipment costs are high, the equipment is large, and equipment operating costs are high because the process must be performed in a vacuum, and heat and pressure must also be applied in a vacuum for bonding.
Furthermore, with the bonding method taught in Japanese Unexamined Patent Publication (kokai) H1-2705741 (1989-270574), the ceramic must be immersed in a liquid halide-fluoride bath, and heated for an extended time at 700.degree. C. to 1100.degree. C. to deposit a non-oxide surface layer. This process is both difficult and time-consuming, and is only suitable for bonding a limited range of materials, that is, a ceramic to a ceramic, or a ceramic to a metal.
The bonding method taught in Japanese Unexamined Patent Publication (kokai) H10-36145 (1998-36145) works by dissolving bonding members of which a primary constituent is silicon dioxide in hydrofluoric acid. As a result, in addition to being extremely limited in the range of materials with which it can be used, this method requires much time for bonding, and is not easy to use because of the use of a hydrofluoric acid solution in the bonding process.
The above-noted method for bonding by means of pyrolizing a fluoride gas in a high temperature environment requires that the entire process be completed at a high temperature, and therefore requires a high temperature oven. As a result, equipment costs are high, the process can only be applied with chrome and other high melting point materials, and cannot be used with low melting point materials.